Which is a liquid fossil feul

What must be true for natural selection to heppen

What are the formed elements (cell or parts of cell) in blood and what are their functions ?

Johnny rode his bike to a friend's house 4 blocks down the street in his neighborhood. he immediately rode back home once he realized his friend was not able to play. what was his displacement for the total bike ride? how did you determine this? what could we use as a reference point to determine he was in motion during his bike ride? why can you use it as a reference point